That's right, the app requires an Office 365 subscription, before allowing you to view and edit Powerpoint, Excel, and Word files which are stored on the cloud or attached to emails. You can also edit recently used files offline, and create Word and Excel documents from scratch on your device.

The app is available for iPhone and iPod Touch, and requires iOS 6.1 or later. iPad support is curiously absent—especially given that it would be a more natural device for document editing—and the app is currently only available in the US. Why no iPad? Likely because Microsoft would rather steer people to its web apps (which are, incidentally, not very iPhone-friendly).

As exciting as it is to finally see Office and iOS merge, the subscription point is a bit of a disappointment, although the silver lining is that your iPhone won't count as one of your five total installations.